The present invention relates to a display device which utilizes the emission of electrons into a vacuum in response to application of an electric field; and, more particularly, the invention relates to a field emission type display device, which is formed by laminating a back substrate, on which a large number of cathode lines and a large number of control electrodes constituting an electron emission mechanism are formed, and a front substrate, on which phosphors and anodes are formed.
As a display device which exhibits a high brightness and a high definition, color cathode ray tubes have been widely used conventionally. However, along with the recent request the higher quality in the generation of images in information processing equipment or television broadcasting, there has been an increased demand for planar displays (panel displays), which are light in weight and require a small space, while exhibiting a high brightness and a high definition.
As typical examples, liquid crystal display devices, plasma display devices and the like have been commercialized. Further, as display devices which can realize a higher brightness, it is expected that various kinds of panel-type display devices, including a display device which utilizes the emission of electrons from electron emitting sources into a vacuum (hereinafter, referred to as “an electron emission type display device” or “a field emission type display device (FED)”), and an organic EL display device (OLED) which is characterized by low power consumption, will be commercialized.
Among such panel type display devices, there are various types of field emission type display devices, including a display device having an electron emission structure as developed by C. A. Spindt et al, a display device having an electron emission structure of a metal-insulator metal (MIM) type, a display device having an electron emission structure which utilizes an electron emission phenomenon based on a quantum theory tunneling effect (also referred to as a “surface conduction type electron emitting source), and a display device which utilizes an electron emission phenomenon possessed by a diamond film, a graphite film and carbon nanotubes and the like.
The field emission type display device includes a back panel, on which cathode lines having electron-emission-type electron sources and control electrodes are formed on an inner surface thereof, and a front panel, on which anodes and phosphors are formed on an inner surface which faces the back panel; wherein, both panels are laminated to each other by inserting a sealing frame between the inner peripheries of both panels, and the inside space thereof is evacuated. Further, to set a distance between the back substrate and the front substrate to a given value, distance holding members are provided between the back panel and the front panel in places where there are neither cathode lines nor control electrodes.
The back panel includes a plurality of cathode lines and control electrodes, which constitute electron sources, on a back substrate, which is preferably made of glass, alumina or the like. The cathode lines extend in a first direction and are juxtaposed in a second direction in a large number on the back substrate. The control electrodes are insulated from the cathode lines and are arranged in the vicinity of the cathode lines. The control electrodes extend in the second direction and are juxtaposed in the first direction in a large number. At a crossing portion of a cathode line (the electron source provided to the cathode line) and a control electrode, one pixel (a unit pixel in a monochromatic display) or one unit pixel (in case of color display, one color pixel being constituted of three unit pixels of, for example, red (R), green (G), blue (B)) is formed, wherein one pixel implies each unit pixel of R, G, B (hereinafter, these elements are referred to as a pixel as a general term). The emission quantity (including ON/OFF states) of electrons from the electron source is controlled in response to the potential difference between the cathode lines and the control electrodes.
On the other hand, the front panel includes anodes and phosphors disposed on the front substrate, which is formed of a light transmitting material, such as glass or the like. The inside space between panels, which is sealed by a sealing frame, is evacuated to a vacuum of 10−5 to 10−7 Torr, for example. Each control electrode includes electron passing apertures at each crossing portion of a cathode line and a control electrode, wherein electrons which are emitted from the electron source of the cathode line are allowed to pass through the electron passing apertures to the anode side. The electron source is constituted of, for example, a carbon nanotube (CNT), diamond-like carbon (DLC), a so-called Spindt, or other electric field emission cathode (hereinafter also simply referred to as a cathode).
The cathode lines are juxtaposed with each other with a gap therebetween. Further, the control electrode is constituted of a plate-like thin metal plate, a metal mesh or a metal vapor deposition film having electron passing apertures. In case of the metal mesh, mesh holes constitute the electron passing apertures. In case of the metal vapor deposition film, an insulating layer is formed between the cathode line and the metal vapor deposition film, and a metal film having the electron passing apertures is vapor-deposited. The insulating layer at a portion of the electron source which corresponds to the electron passing apertures is removed.